1. Field of the Invention
This invention relates to an apparatus for developing an electrostatic latent image, and more particularly to an apparatus for developing an electrostatic latent image into a toner image in which the thickness of a toner layer used for forming the toner image is controlled by use of a doctor blade to control the density of the toner image.
2. Description of the Prior Art
In a touch down development of a donor development method of electrostatography in which an electrostatic latent image is developed into a toner image by use of a toner carried by a developing roller and the toner image is transferred to a paper or the like or is used as a final image, the image density changes with the thickness of the layer of the toner carried by the developing roller. The thickness of the toner layer is controlled, for instance, by use of a doctor blade projected toward the surface of the developing roller. A part of the toner layer on the developing roller is scraped off by the edge of the doctor blade to obtain the desirable thickness of the toner layer.
The above described apparatus using a doctor blade for controlling the thickness of the toner layer, however, has a defect in that the toner scraped off is liable to stick to the tip of the doctor blade, which results in formation of scratches or lines on the surface of the toner layer and deteriorates the quality of the toner image obtained.